Locomotive excitation and regenerative braking control arrangement

ABSTRACT

An electric locomotive is provided with drive motors driving a generator whose rectified output is combined with the current supplied the drive motors to power the locomotive&#39;&#39;s tractional motors. Regenerative braking is effected when the tractional motors are operated as generators to power one of the drive motors which in turn drives the other drive motors as generators to return power to the supply line. The current supplied by the several tractional motors to the powered drive motor is balanced by including, in alternative embodiments, resistors or feedback in the tractional motor circuits.

U United States Patent 1191 1111 3,743,901 Joh son July 3, 1973LOCOMOTIVE EXCITATION AND 1,246,424 11/1917 Hellmund 318/87 REGENERATIVEBRAKING CONTROL 111891193 6/1916 ARRANGEMENT 1,411,419 4/1922 1,358,58011/1920 Rouviere 318/86 [75] inventor: Lauren L. Johnson, Westchester,lll.

Prima Examiner-T. E. L nch 73 '3 Y 1 I Asslgnee 3:1 :53 CorporationAttorney-E. W. Chnsten and C. R. Meland 22 Filed: Nov. 15, 1971 ABSTRACTAppl. No.: 198,771

An electric locomotive is provided with drive motors driving a generatorwhose rectified output is combined with the current supplied the drivemotors to power the locomotives tractional motors. Regenerative brakingis effected when the tractional motors are operated as generators topower one of the drive motors which in turn drives the other drivemotors as generators to return power to the supply line. The currentsupplied by the several tractional motors to the powered drive motor isbalanced by including, in alternative embodiments, resistors or feedbackin the tractional motor circuits.

3 Claims, 2 Drawing Figures LOCOMOTIVE EXCITATION AND REGENERATIVEBRAKING CONTROL ARRANGEMENT This invention relates to an electriclocomotive circuit arrangement for supplying tractional motors duringnormal operation and for providing regenerative braking.

Electric locomotives include tractional motors to drive locomotivewheels during locomotive operation. A variety of excitation circuits arepossible to supply power to the tractional motors. In the instantinvention, an auxiliary generator is driven by drive motors suppliedfrom an overhead right-of-way .power supply. Current from theright-of-way through the drive motors is combined with current suppliedby the generator to power the tractional motors, thus reducing the dutyon both the generator and the drive motors.

For locomotive braking in the instant system, regeneration is effectedin which one of the drive motors is supplied electrical power from thetractional motors operating as generators. The powered drive motordrives the remaining drive motors as generators to return power to theright-of-way power system. To balance the current of the tractionalmotors during regeneration, two alternative circuit arrangements aredisclosed. Resistors can be included in series with the tractionalmotors when operating in the braking mode or current feedback can beprovided to achieve the requisite load balance.

In the instant invention, two modes of operation are provided for thetractional motors of an electric locomotive. In the first mode, thetractional motors are powered to enable them to drive the locomotive; inthe second mode, braking is accomplished with the tractional motorsoperating as generators. The drive motors and the generator whichcooperate to supply the tractional motors during normal power operationare required during regenerative braking to perform functions differentfrom those performed during power operation. in particular, all but oneof the drive motors operates as a generator in the regenerative brakingmode. This reversal of operating functions with regard to the tractionalmotors and the drive motors permits power to be returned to theright-ofway power supply during braking.

Accordingly, it is an object of the present invention to provide a drivearrangement for an electric locomotive including regenerative brakingwherein a generator supplies field excitation to tractional motorsprovided with resistors or feedback to balance the tractional motorarmature current during regenerative braking and wherein all but one ofa plurality of drive motors are driven as generators to return power toa right-ofway supply line and wherein the one drive motor not operatedas a generator is energized by the tractional motors to drive theremaining drive motors.

Other objects, advantages, and features of the invention will becomemore readily apparent as reference is had to the accompanyingspecification and drawings wherein:

PEG. 1 is a circuit schematic for an electric locomotive drive includingregenerative braking according to the present invention wherein loadbalance is provided by resistors included in the armature circuits ofthe tractional motors during regenerative braking; and

FIG. 2 is a circuit schematic for an electric locomotive drive includingregenerative braking according to the present invention wherein loadbalance is provided by a feedback connection operative duringregenerative braking.

Reference should now be made to FIG. 1 wherein an electric locomotivedrive and braking circuit is shown including six tractional motors 10,12, l4, 16, 18, and 20 coupled respectively with wheels (notillustrated) of the locomotive. The electric locomotive receives powerfrom a 3,000 volt DC overhead right-of-way supply 22. The right-of-wayis of a type generally known for powering electric locomotives and,accordingly, details are neither shown nor discussed.

The overhead power. supply 22 is used to energize four drive motors 24,26, 28, and 30 mechanically coupled through linkage 32 to adynamoelectric generator 34. The mechanical linkage 32 interconnects thefour drive motors during all operation in the power or braking modes.This linkage can take a variety of known forms and is accordinglyneither shown nor discussed in detail.

The four drive motors are equipped with separate field windings suppliedfrom an auxiliary locomotive source (not shown) for controlled speedoperation. The motors may also be equipped with series cumulative fieldsor separately excited fields supplied directly from the right-of-way.The alternatives regarding field control for the drive motors areconventional and generally known for electric locomotives. Accordingly,no detailed field arrangement is set forth or discussed.

The generator 34 includes an output winding connected in either a Deltaor Y configuration depending on system conditions and demands. ThisDelta-Y flexi bility is known and therefore, the circuit schematic doesnot include details. A field winding of the generator 34 is suppliedfrom an auxiliary source (not illustrated) and is controllable in aconventional manner as is done with generally known diesel electriclocomotives. As with the other conventional controls cited herein, thegenerator field and its associated circuitry are not shown or discussedin detail.

A full-wave bridge rectifier 36 is connected with the output from thegenerator 34 and provides a DC voltage between the lines 38 and 40. Thisrectified output from the generator has a voltage and current capabilitydetermined by the operation of the generator 34 and its related control.

A switch 42 controls a plurality of movable contacts denoted C and amovable contact C-50 to afford selection of a power mode or a brakingmode. As shown in the schematic, the movable contacts engage theirrespective associated fixed contacts M to provide a motoring mode; whenthe movable contacts engage the fixed contacts B, the braking mode isselected.

When normal drive operation is desired, the switch 44 is closedconnecting the drive motors with the 3,000 volt right-of-way through thecurrent limiting resistor 46 and the pick-up member 48. To start theoperation of the drive, the movable contact C-50 must engage theassociated fixed contact B. This can be accomplished by actuating theswitch 42 moving all the movable contacts C to their respective fixedcontacts B or by independent regulation of the movable contact 050.

When the switch 44 is closed and the contact C-50 engages the associatedcontact B, current is supplied the drive motors accelerating them andinitiating operation by the generator 34. As the drive motorsaccelerate, the current therethrough subsides and the current limitingresistor 46 is removed from the circuit by closing the switch 52. Thisswitch is controlled by the current or speed of the drive motors toremove the current limiting resistor at the desired time. The requisitesensing and control for this switch are generally known and are notshown or described in detail. Ths switch C-50 is also moved from theassociated contact B to the associated contact M when the currentthrough the drive motors is reduced to a predetermined level or when thespeed attains a preset value. As noted for the switch 52, the requisitesensing and control are conventional.

Each tractional motor is supplied current from the line 38 through anassociated diode D, 12D, MD, 16D, 18D, or 20D. The current path for eachmotor continues through the respective motor, a first movable contact ofthe switch 42, the associated winding 10W, 12W, 14W, 16W, 18W, or 20W,and a second movable contact of the switch 42 to the line 40.

The current supplied from the generator 34 through the bridge 36 isaugmented by the current through the drive motors which is connected tothe diodes 10D, 12D, 14D, 16D, 18D, and 20D through the movable contact050. In this manner, the duty on the motors and the generator 34 isminimized by virtue of the combined excitation of the tractional motors:the tractional motors receive a portion of their excitation directlyfrom the overhead supply 22 through the drive motors and a portion fromthe generator 34.

When it is time to initiate braking of the tractional motors, the switch42 is positioned such that all the movable contacts engage theirrespective fixed contacts denoted B. At this time, the respectivetractional motors are driven as generators with their field windings110W, 12W, 14W, 16W, 18W, and 20W serially connected across the voltagebetween lines 38 and 40. Armature current from the tractional motors iscarried by the diodes 10E, 12E, ME, ME, 18E, and 2015 through thecurrent balancing resistors 10R, 12R, MR, MR, 18R, and 20R to energizethe single drive motor 30. The return path for the current supplied thedrive motor 330 is through the movable contact (3-50 to the respectivetractional motor. The resistors included in the armature circuitsprovide for balance in the annature currents of the various tractionalmotors. Current variations result from differences among the motors ordifferences in locomotive wheel size and the associated motorwheelinterconnections and must be eliminated during regeneration. The recitedload balancing is necessary to ensure uniform loading of all thetractional motors to maximize braking; otherwise, one tractional motorcould be overloaded while another was unloaded. Typically, the balanceresistors have a low resistance: a tractional motor having a 1,000 amprating would require a resistor having a resistance on the order of 0.2ohms.

it should be observed that the diodes 10D, 12D, MD, 16D, 18D, and20D arereverse biased during regeneration thereby preventing currents fromcirculating in the armature circuits. In addition, it should beunderstood that the diodes 10E, 12E, 14E, 16E, ME, and 20E are reversebiased during normal operation to prevent current from by-passing thedrive motor 30.

The mechanical linkage 32 couples the driven motor 30 with the remainingdrive motors and the generator 3 The generator 34 is operated as in thepower mode to develop DC voltage between the lines 38 and 40. The threedrive motors 24, 26, and 28 are provided excitation so that they areoperated during regenerative braking as generators driven by the motor30 and developing power to be returned through the pick-up member 48 tothe overhead supply. The current path for power returned to the overheadsupply includes a path to ground through the motor 30 and the movablecontact (3-50. From the foregoing description, it should be appreciatedthat the generator 34 is operative to provide drive power or fieldexcitation to the tractional motors during power operation or braking,respectively. The drive motors 24, 26, 28, and 30 are all operated asmotors during power operation, whereas only drive motor 30 is operatedas a motor during braking, the other three being operated as generatorsto return power to the supply line.

it should be understood that the windings 10W, 12W, 14W, 16W, 118W, and20W can be provided with reversing means to permit reverse drive of thelocomotive. This provision is conventional and without significance tothe present invention; the above operation applies equally to eithermode of operation.

Reference should now be made to FIG. 2 wherein an alternative embodimentfor the electric locomotive is set forth. Notations used in FIG. l areapplied to common elements of the two circuit arrangements. Accordingly,the tractional motors l0, l2, 14, 16, 18, and 20 are driven by powerfrom the overhead right-of-way 22 connected with drive motors 24, 26,28, and 30. These drive motors are interconnected and connected througha mechanical coupling means or linkage 32 with the generator 34. Thefull-wave bridge 36 provides a DC output between lines 38 and 40 forcontrollable connection with the tractional motors. A mode selectorswitch 42' controls a plurality of movable contacts denoted C' and amovable contact C'-50 in a manner analogous to the control afforded bythe switch 42.

When operation is initiated, the switch 44 is closed to supply the drivemotors through the current limiting resistor 46 and the pick-up 48. Themovable contact C-50 must engage its associated fixed contact 18 tocomplete the excitation circuit for the drive motors. in a mannersimilar to the operation recited above for the movable contact (3-50 atthe outset of locomotive operation, the switch 32 can be actuatedcausing all movable contacts associated therewith to engage theirbraking contacts B so that the movable contact 0-50 engages itsassociated fixed contact B or the requisite connection for the contactC'-50' can be otherwise obtained.

After the current subsides during speed build-up, the switch 52 isclosed as discussed above. in a similar manner, the circuit through themovable contact C50 and its associated contact B is opened in responseto speed or current as discussed with regard to the movable contact 050of FIG. E. It should be noted that the movable contact C'-50 does notengage any fixed contact during motor operation. As shown in thedrawing, only one of the movable contacts C has both a fixed contact Mand a fixed contact B. All the movable contacts C engage theirrespective fixed contacts B during braking or starting effected by theswitch 42'. However, only one movable contact C engages a fixed contactM during normal motor operation; all the other movable contacts C areopen circuited during normal motor operation.

A diode 54 provides a path for current from the overhead 22 through-thedrive motors to the tractional mo tors. As for the system of FIG. 1, thecurrent from the drive motors is combined with current from thegenerator 34 at the tractional motors during normal motor operation.

when the braking mode is selected, the tractional motor windings W, 12W,14W, 16W, 18W, and 20W are connected in shunt across the voltage betweenthe lines 38 and 40 by the switch 42. The tractional motors operate asgenerators driving the single drive motor 30 through a circuit pathincluding a diode 56 and the movable contact C '-50'. Current balanceduring regenerative braking is maintained in this embodiment inaccordance with feedback of armature current. The cur rent feedbackbalance control is readily understood in view of the fact that thecurrent from the bridge 36 has a sense opposite to the associatedarmature current in each of the field windings.

The process of returning power to the overhead supplyfor the FIG. 2arrangement is the same as that discussed for FIG. 1. The motor 30drives the remaining drive motors and the generator 34 through thelinkage 32, and the drive motors 24, 26, and 28 operate as generators toreturn power to the overhead supply. The current path to ground for thepower returned to the overhead supply includes the motor 30 and themovable contact C'-50' and its associated fixed contact B.

Although the foregoing has proceeded in terms of particular embodimentsof the present invention, it should be understood that various changesand modifications could be engrafted thereon by one skilled in the artwithout exceeding the spirit and scope of the appended claims.

1 claim:

1. A power control system for the traction motors of an electriclocomotive operable to provide power and regenerative braking modes ofoperation for said motors comprising, a right-of-way source of directvoltage, a plurality of direct current traction motors operable whenenergized to provide motive power for said locomotive, each tractionmotor having a field winding, a plurality of series connected drivemotors, a generator having a direct voltage output, means mechanicallyconnecting said drive motors and said generator, switching means havinga first position for operating said traction motors in a power mode anda second position for operating said traction motors in a regenerativebraking mode, said switching means in said first position electricallyconnecting said series connected drive motors in series with saidtraction motors across said source of voltage, said switching means insaid first position further electrically connecting said traction motorsacross said generator whereby said traction motors can be suppliedcurrent from said generator and from said source of direct voltagethrough said drive motors, said switching means in said second positionelectrically connecting the field windings of said traction motorsacross said generator whereby said generator supplies current to thefield windings of said traction motors during said braking mode ofoperation, said switching means in said second position furtherelectrically connecting one of said plurality of drive motors acrosssaid traction motors whereby said traction motors when operating asgenerators in said braking mode can supply current to said one drivemotor, said one drive motor during said braking mode mechanicallydriving the other drive motors and said generator whereby said otherdrive motors operate as generators to return power to said source ofdirect voltage and whereby said generator supplies field current to thefield windings of said traction motors, and means for balancing armaturecurrent between respective traction motors when they are operating insaid braking mode.

2. A power control system for the traction motors of an electriclocomotive operable to provide power and regenerative braking modes ofoperation for said motors comprising, a right-of-way source of directvoltage, a plurality of direct current traction motors operable whenenergized to provide motive power for said locomotive, each tractionmotor having an armature and a field winding, a plurality of seriesconnected drive motors, an alternating current generator, rectifiermeans connected to said generator having a direct voltage output, meansmechanically connecting said drive motors and said generator, switchingmeans having a first position for operating said traction motors in apower mode and a second position for operating said traction motors in aregenerative braking mode, said switching means in said first positionelectrically connecting said series connected drive motors in serieswith said traction motors across said source of voltage, said switchingmeans in said first position further electrically connecting saidtraction motors across said rectifier means whereby said traction motorscan be supplied direct current from'said rectifier means and from saidsource of direct voltage through said drive motors, said switching meansin said second position electrically connecting the field windings ofsaid traction motors across said rectifier means whereby said rectifiermeans supplies current to the field windings of said traction motorsduring said braking mode of operation, said switching means in saidsecond position further electrically connecting one of said plurality ofdrive motors across the armatures of said traction motors whereby saidtraction motors when operating as generators in said braking mode cansupply current to said one drive motor, said one drive motor during saidbraking mode mechanically driving the other drive motors and saidgenerator whereby said other drive motors operate as generators toreturn power to said source of direct voltage and whereby said generatorand rectifier means supplies field current to the field windings of saidtraction motors, and a plurality of resistors connected respectively inthe armature circuits of said traction motors during said braking modeto balance armature current among said traction motors.

3. A power control system for the traction motors of an electriclocomotive operable to provide power and regenerative braking modes ofoperation for said motors comprising, a right-of-way source of directvoltage, a plurality of direct current traction motors operable whenenergized to provide motive power for said locomotive, each tractionmotor having an armature and a field winding, a plurality of seriesconnected drive motors, an alternating current generator, rectifiermeans connected to said generator having a direct voltage output, meansmechanically connecting said drive motors and said generator, andswitching means having a first position for operating said tractionmotors in a power mode and a second position for operating said tractionmotors in a regenerative braking mode, said switching means in saidfirst position electrically connecting said series connected drivemotors in series with said traction motors across said source of voltageof operation, said switching means in said second position furtherelectrically connecting one of said plurality of drive motors acrosssaid traction motors whereby said traction motors when operating asgenerators in 8 said braking mode can supply current to said one drivemotor, said one drive motor during said braking mode mechanicallydriving the other drive motors and said generator whereby said otherdrive motors operate as generators to return power 'to said source ofdirect voltage and whereby said generator supplies field current to thefield windings of said traction motors, said armature and field of eachtraction motor be maintained in a series connection during said brakingmode whereby current developed in an armature during regeneration passesthrough a series connected field winding, the sense of said last namedcurrent being opposite to that supplied to said field windings by saidrectifier means. 4

1. A power control system for the traction motors of an electriclocomotive operable to provide power and regenerative braking modes ofoperation for said motors comprising, a right-of-way source of directvoltage, a plurality of direct current traction motors operable whenenergized to provide motive power for said locomotive, each tractionmotor having a field winding, a plurality of series connected drivemotors, a generator having a direct voltage output, means mechanicallyconnecting said drive motors and said generator, switching means havinga first position for operating said traction motors in a power mode anda second position for operating said traction motors in a regenerativebraking mode, said switching means in said first position electricallyconnecting said series connected drive motors in series with saidtraction motors across said source of voltage, said switching means insaid first position further electrically connecting said traction motorsacross said generator whereby said traction motors can be suppliedcurrent from said generator and from said source of direct voltagethrough said drive motors, said switching means in said second positionelectrically connecting the field windings of said traction motorsacross said generator whereby said generator supplies current to thefield windings of said traction motors during said braking mode ofoperation, said switching means in said second position furtherelectrically connecting one of said plurality of drive motors acrosssaid traction motors whereby said traction motors when operating asgenerators in said braking mode can supply current to said one drivemotor, said one drive motor during said braking mode mechanicallydriving the other drive motors and said generator whereby said otherdrive motors operate as generators to return power to said source ofdirect voltage and whereby said generator supplies field current to thefield windings of said traction motors, and means for balancing armaturecurrent between respective traction motors when they are operating insaid braking mode.
 2. A power control system for the traction motors ofan electric locomotive operable to provide power and regenerativebraking modes of operation for said motors comprising, a right-of-waysource of direct voltage, a plurality of direct current traction motorsoperable when energized to provide motive power for said locomotive,each traction motor having an armature and a field winding, a pluralityof series connected drive motors, an alternating current generator,rectifier means connected to said generator having a direct voltageoutput, means mechanically connecting said drive motors and saidgenerator, switching means having a first position for operating saidtraction motors in a power mode and a second position for operating saidtraction motors in a regenerative braking mode, said switching means insaid first position electrically connecting said series connected drivemotors in series with said traction motors across said source ofvoltage, said switching means in said first position furtherelectrically connecting said trAction motors across said rectifier meanswhereby said traction motors can be supplied direct current from saidrectifier means and from said source of direct voltage through saiddrive motors, said switching means in said second position electricallyconnecting the field windings of said traction motors across saidrectifier means whereby said rectifier means supplies current to thefield windings of said traction motors during said braking mode ofoperation, said switching means in said second position furtherelectrically connecting one of said plurality of drive motors across thearmatures of said traction motors whereby said traction motors whenoperating as generators in said braking mode can supply current to saidone drive motor, said one drive motor during said braking modemechanically driving the other drive motors and said generator wherebysaid other drive motors operate as generators to return power to saidsource of direct voltage and whereby said generator and rectifier meanssupplies field current to the field windings of said traction motors,and a plurality of resistors connected respectively in the armaturecircuits of said traction motors during said braking mode to balancearmature current among said traction motors.
 3. A power control systemfor the traction motors of an electric locomotive operable to providepower and regenerative braking modes of operation for said motorscomprising, a right-of-way source of direct voltage, a plurality ofdirect current traction motors operable when energized to provide motivepower for said locomotive, each traction motor having an armature and afield winding, a plurality of series connected drive motors, analternating current generator, rectifier means connected to saidgenerator having a direct voltage output, means mechanically connectingsaid drive motors and said generator, and switching means having a firstposition for operating said traction motors in a power mode and a secondposition for operating said traction motors in a regenerative brakingmode, said switching means in said first position electricallyconnecting said series connected drive motors in series with saidtraction motors across said source of voltage with the armature andfield of each traction motor connected in series, said switching meansin said first position further electrically connecting said tractionmotors across said rectifier means whereby said traction motors can besupplied current from said rectifier means and from said source ofdirect voltage through said drive motors, said switching means in saidsecond position electrically connecting the field windings of saidtraction motors across said rectifier means whereby said rectifier meanssupplies current to the field windings of said traction motors duringsaid braking mode of operation, said switching means in said secondposition further electrically connecting one of said plurality of drivemotors across said traction motors whereby said traction motors whenoperating as generators in said braking mode can supply current to saidone drive motor, said one drive motor during said braking modemechanically driving the other drive motors and said generator wherebysaid other drive motors operate as generators to return power to saidsource of direct voltage and whereby said generator supplies fieldcurrent to the field windings of said traction motors, said armature andfield of each traction motor be maintained in a series connection duringsaid braking mode whereby current developed in an armature duringregeneration passes through a series connected field winding, the senseof said last named current being opposite to that supplied to said fieldwindings by said rectifier means.